UGHHH!!! I was so close to a breakthrough in minimap technology, but no, because the standard map size? 64x64... Why won't BGSCALE work for more than 3600 tiles - less than the map editor lets you create??

you can make BG layers bigger than 3600 tiles (in fact, the limit is 16383), but the internal renderer can only display a maximum of 3600 tiles on screen at one time.